Title:

Evaluation of the Implementation of Portsmouth Stormwater BMPs

The water quality in the Great Bay has been declining due to the excess nutrient loading from non-point source and wastewater treatment facility effluent. To combat this issue in an attempt to improve the water quality in the Great Bay, the EPA issued an MS4 Stormwater permit and a Great Bay permit to Portsmouth. These permits state that Portsmouth must either reduce their nitrogen load in the stormwater treatment system effluent to 3 mg/L, or reduce the nitrogen load via non-point sources by 45% over the next three years, and 11% over the first five years. Portsmouth decided to take an adaptive management approach and investigate the nitrogen removal ability currently installed in the form of stormwater best management practices (BMPs). To quantify nitrogen load removal, data was collected for 17 different BMPs and entered into the Pollutant Tracking and Accounting Program (PTAP). Data collected included the physical storage capacity of the system to hold water, drainage area, area of impervious cover, soil type, and BMP type. PTAP utilized the input data for each system and quantified pollutant loads in pounds per year. This pollutant load data was utilized to make recommendations to the City of Portsmouth for future BMP installations. It was also used to calculate how far along Portsmouth is in reducing their nitrogen load via non-point sources and compared to the permit requirements. A cost comparison was conducted to determine whether it was worth it financially for Portsmouth to pay to evaluate the current systems in the ground when compared to the cost of wastewater treatment plant upgrades. This project helped inform Portsmouth on how to proceed with treating stormwater to satisfy the two permits. The work conducted in this project will continue with Portsmouth collecting data and quantifying pollutant load removal for the remaining systems that were not investigated over the course of this project.

Name

Comment*

Comments are viewable only by submitter

Captcha*